Drug delivery stent

ABSTRACT

The drug delivery stent assembly includes a hollow tubular wire stent which extends in a path defining a generally cylindrical envelope and which has side walls facing outwardly of the cylindrical envelope with holes therein for delivery of liquid to a site in a vessel where the stent is placed and the stent being constructed in a manner which permits the stent to be placed in one of two states, one state being where the stent assumes the shape of an enlarged generally cylindrical envelope and the other state being where the stent assumes the shape of a contracted smaller cylindrical envelope.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a retrievable drug delivery stent whichis made of a hollow tubular wire and which can be carried on a balloonof a balloon catheter to a site of a stenotic lesion where the stent isimplanted. Subsequently, a balloon catheter can be inserted into thearea of the stenotic lesion and a balloon can be positioned within thestent and by heating or cooling the stent with fluid supplied to theballoon, causing the stent to take another form, namely a retractedform. Then the stent and balloon can be removed. The hollow tubular wirestent is preferably made of a metal, such as stainless steel, tantalumor perhaps even from a nickel titanium alloy sold under the trademarkNitinol which can assume different shapes based upon the temperature ofthe Nitinol™. The tubing has holes therein for delivering a liquidsolution or drug to a stenotic lesion. The hollow tubular wire stentalso can be made of a plastic material.

2. Description of the related art including information disclosed under37 C.F.R. 21211.97-1.99

Heretofore, wire stents have been proposed and one example of anundulating wire stent which extends in an undulating pattern back andforth in circular paths connected by loops to form a generallycylindrical envelope and which is adapted to be received on a balloon ofa balloon catheter for insertion into a blood vessel to a site of astenotic lesion is disclosed in the Gianturco U.S. Pat. No. 5,041,126.

Another example of a wire stent, preferably made of Nitinol™ thatextends in an undulating manner in a helical path in a cylindricalenvelope is disclosed in the Pinchuk U.S. Pat. No. 5,019,090.

A stent delivery system, which includes a sheath that is received abouta balloon carrying a stent for facilitating insertion of the assembly ofthe sheath, stent, and balloon on a wire guidewire to a site of astenotic lesion is disclosed in the Lau et al. U.S. Pat. No. 5,158,548.

Further, there has been disclosed in the Silverstrini U.S. Pat. No.5,234,456, a hydrophilic stent which can be made of hollow tubularmembers. The hollow walls of the tubular members have hydrophilicmaterial therein containing a drug and are fabricated of asemi-permeable material so that liquid can pass therethrough to swellthe hydrophilic material.

As will be described in greater detail hereinafter, the hollow tubularstent of the present invention extends in a cylindrical envelope about aballoon and has holes therein that face outwardly of the cylindricalenvelope whereby a drug can be delivered to the area of a stenoticlesion through the holes in the hollow wire tubular stent. After thestent is implanted at the site of the stenotic lesion and a fluiddelivery tube is left in place connected to the stent for supplyingliquid thereto, such as a liquid containing a drug, after a short periodof time (a few days to a week or more), a dissolving fluid can beinserted into the liquid delivery tube for dissolving an end portion ofthe tube to disconnect the tube from the stent. Then, a balloon on aballoon catheter or a balloon on a wire guidewire can be reinserted intothe vessel to the area of the stenotic lesion and partially inflated toassist in the withdrawal of the tubular wire stent from the area of thestenotic lesion.

The drug delivered to the area of the stenotic lesion can be of the typewhich dissolves plaque material forming the stenosis or can be ananti-platelet formation drug or an anti-thrombotic drug. Such drugs caninclude TPA, heparin, or urokinase, for example.

SUMMARY OF THE INVENTION

According to the invention, there is provided a drug delivery stentassembly including a wire stent made of a hollow tubular material whichextends in a path defining a generally cylindrical envelope and whichhas side walls facing outwardly of the cylindrical envelope with holestherein for delivery of liquid to a site in a vessel where the stent isplaced and the stent being constructed in a manner which permits thestent to be placed in one of two states, one state being where the stentassumes the shape of an enlarged generally cylindrical envelope and theother state being where the stent assumes the shape of a contractedsmaller cylindrical envelope.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal view, partially in section and partially brokenaway, of a distal portion of a sheath, stent, balloon and ballooncatheter assembly constructed according to the teachings of the presentinvention.

FIG. 2 is an enlarged portion of a helically and undulating extendinghollow tubular wire stent which extends in a cylindrical envelope aroundthe balloon shown in FIG. 1 and shows holes in the outwardly facingportions of the tubular wire stent in accordance with the teachings ofthe present invention.

FIG. 3 is a longitudinal view, partially in section and with portionsbroken away, of a blood vessel within which the stent is implanted.

FIG. 4 is an enlarged view with portions broken away and partially insection of the connection of a proximal end of the tubular wire stent tothe distal end of a liquid delivery tube and shows, in phantom, ahypodermic needle which can be inserted into a distal end portion of theliquid delivery tube for supplying liquid to the tubular wire stent.

FIG. 5 is a perspective view of another configuration for a hollowtubular wire stent which can be used in place of the undulatinghelically extending stent shown in FIGS. 1, 2 and 3.

FIG. 6 is a perspective view of another configuration for a hollowtubular wire stent, namely a coiled wire spring type configuration,which can be used in place of the stents shown in FIG'S. 1 and 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to the drawings in greater detail, there is illustrated inFIG. 1 a stent delivery system 10 constructed according to the teachingsof the present invention and including a hollow metal tubular wire stent12 which can made of stainless steel, tantalum or even from a formablematerial, such as a nickel titanium alloy sold under the trademarkNitinol and which extends in an undulating manner in a helical patharound a balloon 14 of a balloon catheter 16 or a balloon on a wire(BOAW) guidewire 16. The BOAW guidewire 16 includes a catheter 18, theballoon 14 and, at its distal end, a highly flexible coiled spring wiretip 22. Proximal to the coiled spring wire tip 22 and mounted on thecatheter 18 is the balloon 14. The remainder of the catheter 18 extendsproximally to a steering mechanism and an infusion port (not shown) forsteering the BOAW guidewire 16 to a site of a stenotic lesion and forenabling an inflating liquid to be supplied to the balloon 14.

According to the teachings of the present invention, mounted on theballoon 14 is the hollow metal tubular wire stent 12 which extends in anundulating manner in a helical path around the balloon 14 therebydefining a generally cylindrical envelope surrounding the balloon 14.

Also according to the teachings of the present invention, a liquiddelivery tubing 24 has a distal end portion 25 fixed to a proximal end26 of the hollow metal tubular wire stent 12. It will be understood thata distal end 27 of the stent 12 is closed. On the portions 28 of thehollow metal tubular stent 12 which are on the outside of thecylindrical envelope that the stent 12 defines, there are formed, suchas with a laser beam, small ports or holes 29 in the tubular stent 12whereby liquid can be dispensed from those holes 29 to the area of thestenotic lesion.

If desired and as shown, a sheath 30 can be provided surrounding thestent 12 on a balloon 14 shown in FIG. 1 to facilitate tracking of thesheath 30, stent 12, balloon 14 and balloon on wire a guidewire 16through a blood vessel 32 (FIG. 3) to a site of a stenotic lesion.

The sheath 30 can be of the type disclosed in Lau et al. U.S. Pat. No.5,158,584 or can be of the type disclosed in co-pending application Ser.No. 08/203,805 filed on Mar. 1, 1994 and entitled STENT DELIVERY SYSTEM,now U.S. Pat. No. 5,453,090 granted Sep. 26, 1995.

FIG. 2 illustrates in larger detail the holes 29 that are formed inouter facing sides 28 of the hollow metal tubular stent 12.

FIG. 3 shows the stent in a blood vessel 32 after it has been positionedin the blood vessel 32 and the balloon on a wire guidewire 16 has beenwithdrawn and, if a sheath 30 was used, the sheath 30 also has beenwithdrawn.

FIG. 4 is an enlarged fragmentary view, partially in section, of acoupling arrangement 40 between the proximal end 26 of the hollow metaltubular stent 12 and the distal end portion 25 of the liquid/drugdelivery tubing 24 connected to the proximal end 26 of the stent.

In one embodiment of the liquid/drug delivery tubing 24, a plug or seal48 can be provided in the distal end portion 25 of the liquid/drugdelivery tubing 24. Also if desired, just prior to the insertion of thestent 12 and balloon 14 into the blood vessel 32 or into a sheath 30 forintroduction into the blood vessel 32, a hypodermic needle 50, shown inphantom, can be used to penetrate the distal end portion 25 of theliquid/drug delivery tubing 24 to insert a drug therein.

Also, of course, the plug 48 can be eliminated and is only an optionalfeature.

Once the stent 12 is implanted as shown in FIG. 3, a drug, such as adrug that is effective in dissolving plaque in a stenotic lesion, can beinjected through the delivery tubing 24 to the hollow stent 12 and thenout the holes 29 in the outer periphery of the stent 12 for treating thestenotic area.

Other drugs that can be delivered by the stent in a cardiovascularprocedure can include an anti-platelet or platelet inhibiting drug suchas Heparin or an anti-thrombotic drug such as Urokinase or possibly TPA.

Of course the stent 12 with the holes 29 therein can be used fordelivering other medications to the walls and interior of a body vessel.

In one embodiment, the stent 12 can have two states of size or shape,this being effected by using a Nitinol™ material which can have oneshape or state at one temperature and can be caused to take anothershape or state at another temperature. Heat can be supplied by a heatedsaline solution or by body heat.

After a sufficient treatment of the walls of the vessel at the site ofplacement, with a liquid or drug supplied to the hollow stent 12vis-a-vis the liquid/drug delivery tubing 24, a liquid, such as a heatedliquid or a body fluid compatible solvent, can be inserted into theliquid/drug delivery tubing 24, and particularly to the distal endportion 25 thereof to dissolve the connection of the drug deliverytubing 24 to the proximal end 26 of the hollow tubular stent 12 therebyto facilitate retrieval of the drug delivery tubing 24.

At the same time or afterwards, a balloon 14 such as a balloon on a wireguidewire or a balloon 14 on a balloon catheter 16, can be inserted intothe vessel to place the balloon 14 in the area of the stent 12 and theballoon 14 is then inflated to come into contact with the stent 12. Thena liquid having a temperature which will cause a change in state of thehollow metal tubular stent 12 is injected into the balloon 14. Forexample, a saline solution at room temperature can be circulated in apartially expanded balloon 14 adjacent the stent 12 to cause the stentto contract to its smaller shape whereupon the balloon 14 can beinflated slightly to engage the stent 12 and then the balloon catheteror balloon on a wire guidewire 16 can be withdrawn to remove the stent12 from the vessel.

Another type of stent 60 which is similar to the type of stent disclosedin U.S. Pat. No. 5,041,126 is illustrated in FIG. 5. It is to beunderstood, of course, that other shapes of hollow tubular stents 12 canbe utilized and the material from which the hollow tubular stent is madecan be metal or non-metal, i.e., it can be made out of a polymermaterial.

If desired, additional holes 62 can be provided in the walls of thestent 60 (or of the other stents disclosed herein) that open into lumenof the blood vessel as shown in FIG. 5. Such holes 62 would typically belocated at a distal end or proximal end of the stent, preferably at theupstream end of the stent relative to the liquid flow through thevessel.

The stent can have a coiled spring shape, i.e., such as the stent 70shown in FIG. 6 having holes 72 in an outer wall thereof, as opposed tothe shape of the stent 12 and the shape of the stent 60.

Typically the hollow tubing from which the stent 12, 60 or 70 is madehas an outer diameter of 0.008 inches±0.002 inches and an inner diameterof 0.005 inches±0.002.

The stent must have a length which enables it to be balloon deployable,i.e. 1.5 centimeters for a 2 centimeter length balloon. A coiled springtype stent 70 will then have a length of 8-12 inches when uncoiled.

Furthermore, the stent, e.g. the stent 12, the stent 60 or the stent 70can be a permanently implanted stent. As shown in FIG.6, the stent 70can be a coiled stent made out of a material such as stainless steel ortantalum which does not change shapes with temperature changes, butwhich can be retrieved into a sheath, such as the sheath 30, byutilizing the liquid delivery tubing 24 as a tether. In this respect,the sheath 30 can be moved adjacent to the stenotic site and the coiledstent 70 can then be pulled into the sheath 30.

It will be understood that as a coiled spring type stent 70 sheath ispulled, it stretches slightly and contracts in diameter slightly suchthat during pulling it has a smaller outer diameter than when implantedto facilitate its removal.

Also a partially inflated balloon of a balloon catheter can be insertedinto and within the envelope of the coiled stent 70 before, as it isbeing pulled into, or after it is pulled into, the sheath 30 followed byinflating the balloon to the inner diameter of the stretched coiledspring stent so that the balloon catheter can be used to assist inwithdrawing the stent from the blood vessel.

From the foregoing description it will be understood that theretrievable drug delivery stent 12, 60 or 70 of the present inventionhas the advantage of the use of a temporarily implanted hollow tubularstent 12, 60 or 70 that serves not only as a stent 12, but also as adelivery system for delivery of a drug solution vis-a-vis the holes orpores 29 (and holes 62 or 72 if provided) that are laser drilled intothe stent 12, 60 or 70. Preferably the stent 12, 60 or 70 is made ofNitinol™. Contraction or expansion of the stent 12 is facilitated byutilizing the shape memory of Nitinol™ to cause the stent 12 to collapseback onto a retrievable balloon catheter upon exposure to temperaturesin excess of 50° C. as with the ACT Eigler-Litvack HARTS device.

However the stent 12, 60 or 70 can be manufactured of any materialincluding stainless steel or tantalum so long as the stent 12, 60 or 70is retrievable. The hollow nature of the stent 12, 60 or 70 allows thestent 12, 60 or 70 to be loaded at the time of implantation with asolution of whatever drug the user wishes delivered. The solution thenis delivered via the pores or holes 29 drilled at substantiallyequidistantly spaced intervals over the outer surface of the stent 12,60 or 70. The pores or holes 29 are the size that is small enough toprevent rapid leakage, but large enough to allow slow leakage ofsolution over a period of several days to a week.

Also from the foregoing description, it will be apparent thatmodifications can be made to the retrievable drug delivery stent 12, 60or 70 of the present invention without departing from the teachings ofthe invention. Accordingly, the scope of the invention is only to belimited as necessitated by the accompanying claims.

We claim:
 1. A drug delivery stent assembly including a hollow tubularmetal wire stent which extends in a path defining a generallycylindrical envelope and which has side walls facing outwardly of thecylindrical envelope with holes therein for delivery of liquid to a siteof placement in a vessel where the stent is placed and said stent beingconstructed in a manner which permits said stent to be placed in one oftwo states, one state being where said stent assumes the shape of anenlarged generally cylindrical envelope and the other state being wheresaid stent assumes the share of a contracted smaller cylindricalenvelope.
 2. The drug delivery stent of claim 1 wherein said stent ismade of a nickel titanium alloy.
 3. The stent of claim 1 wherein saidholes are formed with a laser and are small enough to prevent rapidleakage, but large enough to allow slow leakage of a liquid solutionfrom said stent over a period of several hours to a week or more.
 4. Thestent of claim 1 wherein said hollow tubular wire stent extends in anundulating helical path to form the cylindrical envelope.
 5. The stentof claim 1 wherein said hollow tubular wire stent extends back and forthin an undulating manner and in a cylindrical fashion and axiallyforwardly to the distal end of the stent to form a continuous stentdefining a cylindrical envelope (FIG. 3 or FIG. 5) thereby forminggenerally cylindrical undulating loops (FIG. 3 or FIG. 5).
 6. The stentof claim 1 wherein said hollow tubular wire stent extends in a helicalor coiled spring path to form a coiled spring type stent definingtherein the cylindrical envelope.
 7. The stent of claim 1 being made ofstainless steel.
 8. The stent of claim 1 being made of tantalum.
 9. Thestent of claim 1 having at least two holes in the sidewalls of the stentfacing inwardly of the cylindrical envelope near at least one end of thestent.
 10. The stent of claim 1 wherein said hollow tubular wire has anouter diameter of 0.008 inches±0.002 inches and an inner diameter of0.005 inches±0.002.
 11. A drug delivery stent assembly including ahollow tubular wire stent which extends in a path defining a generallycylindrical envelope and which has side walls facing outwardly of thecylindrical envelope with holes therein for delivery of liquid to a siteof placement in a vessel where the stent is placed and said stent beingmade of a material which can be caused to assume two states, one statebeing where said stent assumes the shape of an enlarged cylindricalenvelope and the other state being where said stent assumes the shape ofa contracted smaller cylindrical envelope.
 12. A drug delivery stentassembly including a hollow tubular wire stent which extends in a pathdefining a generally cylindrical envelope and which has side wallsfacing outwardly of the cylindrical envelope with holes therein fordelivery of liquid to a site of placement in a vessel where the stent isplaced and said stent being made of a nickel titanium alloy.
 13. A drugdelivery stent assembly including a hollow tubular wire stent whichextends in a path defining a generally cylindrical envelope and whichhas side walls facing outwardly of the cylindrical envelope with holestherein for delivery of liquid to a site of placement in a vessel wherethe stent is placed and said stent being made of stainless steel.
 14. Adrug delivery stent assembly including a hollow tubular wire stent whichextends in a path defining a generally cylindrical envelope and whichhas side walls facing outwardly of the cylindrical envelope with holestherein for delivery of liquid to a site of placement in a vessel wherethe stent is placed and said stent being made of tantalum.
 15. A drugdelivery stent assembly including a hollow tubular metal wire stentwhich extends in a path defining a generally cylindrical envelope, whichhas a proximal end and which has side walls facing outwardly of thecylindrical envelope with holes therein for delivery of liquid to a siteof placement in a vessel where the stent is placed, means for couplingand uncoupling said proximal end to a liquid delivery tubing and saidstent being constructed in a manner which permits said stent to beplaced in one of two states, one state being where said stent assumesthe shape of an enlarged generally cylindrical envelope and the otherstate being where said stent assumes the shape of a contracted smallercylindrical envelope.
 16. The drug delivery stent assembly of claim 15wherein said coupling means is made of a dissolvable material.
 17. Adrug delivery stent assembly including a hollow tubular metal wire stentwhich has a proximal end, which extends in a path defining a generallycylindrical envelope and which has side walls facing outwardly of thecylindrical envelope with holes therein for delivery of liquid to a siteof placement in a vessel where the stent is placed, means for couplingand uncoupling said proximal end to a liquid delivery tubing and saidstent being made of a material which can be caused to assume two states,one state being where said stent assumes the shape of an enlargedcylindrical envelope and the other state being where said stent assumesthe shape of a contracted smaller cylindrical envelope.
 18. The drugdelivery stent assembly of claim 17 wherein said coupling means is madeof a dissolvable material.
 19. A drug delivery stent assembly includinga hollow tubular wire stent which has a proximal end, which extends in apath defining a generally cylindrical envelope and which has side wallsfacing outwardly of the cylindrical envelope with holes therein fordelivery of liquid to a site of placement in a vessel where the stent isplaced, means for coupling and uncoupling said proximal end to a liquiddelivery tubing and said stent being made of a nickel titanium alloy.20. The drug delivery stent assembly of claim 19 wherein said couplingmeans is made of a dissolvable material.
 21. A drug delivery stentassembly including a hollow tubular wire stent which has a proximal end,which extends in a path defining a generally cylindrical envelope andwhich has side walls facing outwardly of the cylindrical envelope withholes therein for delivery of liquid to a site of placement in a vesselwhere the stent is placed, means for coupling and uncoupling saidproximal end to a liquid delivery tubing and said stent being made ofstainless steel.
 22. The drug delivery stent assembly of claim 21wherein said coupling means is made of a dissolvable material.
 23. Adrug delivery stent assembly including a hollow tubular wire stent whichhas a proximal end, which extends in a path defining a generallycylindrical envelope and which has side walls facing outwardly of thecylindrical envelope with holes therein for delivery of liquid to a siteof placement in a vessel where the stent is placed, means for couplingand uncoupling said proximal end to a liquid delivery tubing and saidstent being made of tantalum.
 24. The drug delivery stent assembly ofclaim 21 wherein said coupling means is made of a dissolvable material.